18 February 2000

INTERPRETING DATA IS AN UPHILL STRUGGLE

UNDERSTANDING scrapie genotyping results is a hard task.

For this reason it has been criticised, but this is the nature of the disease, says SAC veterinary officer, Brian Hosie.

"Scrapie genotyping is a tool for us to enhance resistance within sheep breeds and hopefully reduce the amount of scrapie.

"Currently it is the best option for control. We are unsure whether the agent causing scrapie continues to survive or is eradicated, but work is ongoing to find this out," says Mr Hosie.

Despite selection of breeding stock being the best method for scrapie control there are drawbacks in putting too much emphasis on scrapie selection. Genotyping is important, but narrowing gene pools as a consequence of stringent selection is undesirable, says Mr Hosie.

Generally it is up to breed societies and individual breeders as to how genotyping is adopted by a particular breed. The more sheep a breed blood tests, the more choice there is and the gene pool is not reduced by selection.

"If only small numbers are tested, there is only a small gene pool to select genetic resistance from. In such cases, selection can be very damaging to the gene pool," says Mr Hosie. &#42